I give a brief overview of our theoretical understanding of blazars. I highlight currently unresolved problems and show how multiwavelength (X-ray and TeV) observation of TeV emitting blazars like Mkn 501 may be particularly useful in constraining emission models. I also note that intergalactic absorption of TeV gamma-rays is a process that can no longer be ignored by blazars modelers and that ...

1 Servicio de Protección Radiológica, Hospital Universitario La Fe. E-mail: [email protected] 2 Servicio de Dosimetría Biológica, Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad Autónoma de Barcelona (U.A.B.). 3 Departamento de Biología Celular, Fisiología e Inmunología Celular (U.A.B.). 4 Departamento de Ingeniería Química y Nuclear, Universidad Politécnica de Va...

The properties of the cosmic microwave background radiation provide unique constraints on cosmological models, i.e. on the content, history, and evolution of the Universe. I discuss the latest measurements of the spectral and spatial properties of the cosmic microwave background radiation. Recent measurements from NASA's Cosmic Background Explorer (COBE) satellite, and from balloon-borne and gr...

Increasing development of mobile communication infrastructure while enhancing availability of the technology raises concerns among the public, who see more cell towers erected each day, about possible health effects of electromagnetic radiations. Thereon, a survey of radio-frequency radiation from 60 GSM base stations was carried out in Tehran, Iran at several places mostly located in major med...

Tangled, primordial cosmic magnetic fields create small rotational velocity perturbations on the last scattering surface of the cosmic microwave background radiation. For fields which redshift to a present value of B0 = 3 x 10(-9) G, these vector modes are shown to generate polarization anisotropies of order 0.1-4 microK on small angular scales (500<l<2000), assuming delta function or a power l...

Important information about the early universe can be obtained from a study of the cosmic background radiation ~CBR! in the microwave range. We study high-order correlation and structure functions of temperature fluctuations collected from the first two years of Differential Microwave Radiometer ~DMR! observations from the Cosmic Background Explorer ~COBE! satellite. The intent is to determine ...

We consider globally hyperbolic flat spacetimes in 2+1 and 3+1 dimensions, in which a uniform light signal is emitted on the r-level surface of the cosmological time for r → 0. We show that the frequency of this signal, as perceived by a fixed observer, is a well-defined, bounded function which is generally not continuous. This defines a model with anisotropic background radiation that contains...

The early stages of the universe evolution are discussed according to the hot big bang model and the grand unified theories. The shortcomings of big bang are summarized and their resolution by inflationary cosmology is sketched. Cosmological inflation, the subsequent oscillation and decay of the inflaton field, and the resulting reheating of the universe are studied in some detail. The density ...

We develop an analytic method and approximations to compute the polarization induced in the cosmic microwave background radiation on a wide range of angular scales by anisotropic Thomson scattering in presence of adiabatic scalar (energy-density) linear fluctuations. The formalism is an extension to the polarized case of the analytic approach recently developed by Hu and Sugiyama to evaluate th...